This is a free open source alternative, the pro version is just a cloudbased PaaS based on the same code.

Here's the GitHub: https://github.com/TryGhost/Ghost

Ghost is free and open-source itself. I find it more pleasant to use than most of the alternatives. Presumably it's financially supported by the official hosting service.

Uh, last I checked ghost was both free and open source if you're self hosting.